2015 Northwest Electric Meter School. A division of Brayden Automation Corp. Introduction to Pulse Metering, Pulse Initiators & Isolation Relays

Transcription

1 2015 Northwest Electric Meter School A division of Brayden Automation Corp. Introduction to Pulse Metering, Pulse Initiators & Isolation Relays August 25, 2015 By William H. Brayden, President Brayden Automation Corp./Solid State Instruments Loveland, CO Overview Pulse Metering Terms and Definitions Pulse Calculations Pulse Initiators and Configurations Pulse Applications Pulse Isolation Relays 1

2 Terms & Definitions Pulse Metering Pulse Pulse Initiator Pulse Constant Ke, PKe, Kh, Kp, Kd, Mp CT Ratio, PT Ratio, Multiplier (TF) Switch and Relay Forms What is Pulse Metering? Pulse Metering is the act of measuring energy usage with a watt hour meter, then converting the measured quantity into electronic increments of a constant known value, known as pulses. Filling & dumping a bucket analogy Common standard of exchanging energy use information between systems Simple and Non proprietary 2

3 What is Pulse Metering? Fundamentally used for two purposes: 1. Counting pulses for energy consumption (Kwh) 2. Timing pulses for determining demand KW = (kilowatt hours X3600) seconds KW = kilowatt seconds seconds Why use Pulse Metering? Two general purposes of pulses: 1.) Interval Data Pulses were the basis for counting and recording usage 2.) Real Time Power Use A method of transferring instantaneous real time energy usage information to other devices without any direct electrical contact 3

4 Why use Pulse Metering? Interval Data uses: Customer Billing 1. Energy charges 2. Demand charges 3. Power Factor charges 4. Load Factor Average Demand/ Peak Demand TOU Rate Studies 1. Survey of energy during specific periods to determine the effect of TOU rate structures. 2. Comparing electric heat to gas usage on apartments Why use Pulse Metering? System Planning 1. Future load growth projections 2. Transformer sizing 3. Assisting with rate structures 4. Load projections Future consideration for substation, transmission construction Customer satisfaction and retention 1. Offering more Services, Real Time Pricing 2. Answering billing questions 3. Reduce their energy costs 4

5 Why use Pulse Metering? Utility Applications 1. Delivering pulses to multiple systems (Wholesale Delivery points) for system control 2. Load Profile Information collection using pulses with external pulse recorder 3. Totalization, Billing & Support of special rate structures 4. Check meter comparison with counting/totalizing register relay 5. AMR Automated Meter Reading meter interface Why use Pulse Metering Customer Applications 1. Energy Management / Demand Control Energy Pulses * End of Interval Pulse TOU Pulse Power Factor Calculation 2. Sub metering 3. To combine meter data with other quantities like inputs from gas, water, temperature, pressure, flow, etc. for Energy Tracking. 4. Pulses can be thought of as the lowest common denominator of instantaneous energy information. Reading pulses is generally universal in the EMS industry. Non proprietary. 5

6 What is a Pulse? In Pulse Metering, Form C (3 wire) Pulse A pulse is defined as the change of state or a transition of the pulse initiator from one state to the opposite state. Toggle Form A (2 wire) Pulse a pulse is a complete cycle of a on state transition, a dwell time, and then transition returning to the off state. Momentary What is a Pulse? Momentary contact closures are normally associated with 2-wire (Form A) systems Toggle closures are normally associated with 3-wire (Form C) systems. 6

7 What is a Pulse? A pulse is directly related to a programmable defined value Ke in solid state meters, or to a disk revolution (Kh) in induction meters. Units are in kilowatt hours or watt hours a pulse represents ENERGY (kwh,kvah,kvarh,etc). Pulses can be generated: mechanically (gears &, cams), optically (reflective, through hole), electronically, (hall effect) semiconductor devices (most common today) NEMA Standard EI 13 A Pulse is an electrical signal which departs from an initial level for a limited duration of time and returns to the original level. (This is incorrect for Form C pulses) Example: A sudden change in voltage or current produced by the opening or closing of a contact. Examples: Handbook for Electricity Metering Closing a two wire (Form A) contact SPST Switch Model Closing one side of a three wire (Form C) contact and simultaneously opening the opposite side SPDT Switch Model 7

8 NEMA Standard EI 13 Pulse devices for electricity metering are the functional units for initiating, transmitting, retransmitting, or receiving electric pulses, representing finite quantities, such as energy, normally transmitted from some form of electricity meter to a receiver unit. Handbook for Electricity Metering NEMA Standard EI 13-1 A pulse initiator is any device, mechanical or electrical, used with a meter to initiate pulses, the number of which is proportional to the quantity being measured. It may include an external amplifier, an auxiliary relay, or both to change the amplitude or waveform of a pulse for re transmission to another pulse device. 8

9 What is a Ke Value? Ke is a representation of the amount of energy (at the pulse generator) in an electronic meter. Generally expressed in kilowatt hours per pulse. Ke value is programmable Example: Ke =.001kwh or 1 wh pulse pulse Also called the Secondary Pulse Constant or Energy Constant Ke assumes 120VAC/5A at the meter Ke does not include the CT*PT multiplier of the customer s metering application. What is Pke? Pke is the Primary Pulse Constant. Also called Final Ke or Ke (final) Pke includes the CT*PT multiplier Pke =Ke X(CT * PT) Pke represents the actual energy (Kwh) consumed per pulse in a specific customer metering application. 9

10 Calculating the Pke Value Example: Given: 120/208VAC service Ke =.001 CTR= 600A:5A = 120 PTR= 1 Pke = Ke X(CT x PT) *or the actual energy value per pulse which is: Pke =.001 Kwh X (120X1) =.120 kwh/pulse or 120 wh/p What is the Pke Value? Some Meter Manufacturers do this differently: Given: 120/208VAC service Kh = 1.8 wh/rev P/R(virtual) = Programmable (default = 24) CTR = 600A:5A = 120 PTR = 1 Pke = KhX(CT*PT) P/R *or the actual energy value per pulse which is: Pke = 1.8/24 X 120 = 9.0 wh/pulse or.009 kwh/p 10

11 How to Set the Ke Value (working backwards) Suppose: Customer requires 32 wh/p 120/208VAC so PTR = 1 CTR = 800A:5A = 160 Ke =Pke /(CT*PT) Ke =. 032 /160 Ke =.0002 kwh Pulse Programming 11

12 Pulse Programming Pulse Programming 12

13 Pulse Programming What is a Kh Value? Kh on an induction meter is the amount of energy measured during one disk revolution. Also called: Disk Constant Watthour Constant Meter Constant Expressed in Watt hours, not kilowatt hours per revolution of the eddy current disk 13

14 What is Kp? Kp is the pulse constant of an induction meter Same as Pke but on an electro mechanical induction meter Not programmable but determined by: Kh Meter Constant CTR Current Transformer Ratio PTR Potential Transformer Ratio Number of transitions per disk revolution: Pulses/Revolution (P/R) or Revolutions/Pulse (R/P) What is the Kp Pulse Constant? Also called PW or PC For calculating the Pulse Constant (Kp): For Pulses/Revolution: Kp = Kh X(CT x PT) P/R For Revolutions/Pulse: Kp = Kh X (CT x PT) XR/P 14

15 What is the Kp Pulse Constant? Example: Kh = 1.8 wh/rev CTR = 600/5=120 PTR = 1 P/R = 4 Kp = 1.8 (120X1) 4 =.054kwh/pulse or 54wh/p Maximizing Resolution Greatest resolution = demand divided by the maximum number of pulses in an interval. Example: Assume 1,000 kw load, 16,383 pulses/interval max, 15 minute demand interval Max Kwh/interval = 1000kW/4 = 250kwh (Kwh/interval)/(# pulses/interval) = 250kwh/16,383 Kwh/pulse (Pke) =.0153kwh/pulse So in this example: Pke = 16wh/pulse 15

16 Accounting for Growth Need to add a fudge factor so the max number of pulses per interval is not exceeded by load growth. (25% headroom) Peak KW = 1000KW/.75 = 1333KW Min Kd = 1333KW/16383 =.0813KW/pulse Min Kd =.082KW or 82 watts/pulse Min Pke =.082 / 4 =.0205 Kwh/pulse (~21wh/pulse) To keep from over ranging interval register, Ke must be greater than the Min Pke/TR or in this case: Ke =>.0205 / 160 = kwh The greater the Ke value, the fewer pulses per interval and the higher the demand can be measured in the interval, but resolution is lower. Insure that the maximum # pulses per interval will not overflow ( saturate ) the interval register. Important: Always round up not down Pulse Rate vs. Pulse Capacity Pulse Rate = the maximum number of pulses per second at which the pulse sending device is nominally rated. Pulse Capacity = the maximum number of pulses that the pulse receiving device can accept in a given period of time (usually a second, an hour or a demand interval). 16

17 Typical Max Pulse Capacity & Rates For old printing demand recorders: Capacity = 999 pulses/interval Max pulse rate = 1.11 pulses/second For old magnetic tape recorders: Capacity = 7200 pulses/hour Max pulse rate around 2 pulses/second For older solid state meters: Capacity = 16,383 pulses/interval (14 bit#) Max Pulse rate around 15 ~ 20 pulses/second Today s solid state meters Capacity = 65,535 pulses/interval (16 bit#) Max Pulse rate around 40 pulses/second Special Notes Pulse constants are usually expressed in 3 wire (Form C) format. Pulse values in 2 wire format are double the pulse value in 3 wire formats. Meter testing with Form C pulse outputs: Connect to either the KY or KZ terminals and then input to the test board. This configuration will only provide ½ the number of pulses for the programmed Ke pulse constant. Ke value must be doubled for a 2 Wire Pulse System 17

18 Pulse Initiators Simply stated a pulse initiator is a switch A device attached to an induction or solid state meter that transmits contact closures as the meter measures energy. Often called a KYZ Switch or KYZ Option Board. Each contact closure or opening (change of state) equals a defined value of energy, generally in kilowatt hours/pulse. Typically used to transmit energy consumption information on a near instantaneous basis to other pieces of equipment which use pulses. Pulse Initiators (aka KYZ switch) Mechanical pulse initiators used with induction meters Single output have a fixed pulse value determined by a watt hour constant (Kh) and gear ratio between the disk and the device. Today s solid state meters allow Multi channel, multi function output boards both the function and operational value of output relays to be programmable. Example: Let relay #1 represent kwh and each pulse = 192 wh Let relay #2 represent TOU time interval signal 18

19 Pulse Types KYZ Energy Pulses (Form C or Form A) EOI End Of Interval (Form A) TOU Time Of Use Signaling (Form A) Alert Peak demand alert Pulse Initiator Form C Simple Switch Model 19

20 Pulse Initiator Form C Simple Switch Model Pulse Initiator Board 20

21 Contact Types Dry Contacts have no electricity applied to them from the device in which they are installed. External voltage is supplied. Electrically Isolated Sourced Voltage Contacts generally have line voltage sourced to Y and Z terminals. Less Frequently Used Used only in special applications where non standard interface is required. Not isolated How Do Dry Contacts Work? Wetting Voltage sense voltage is applied from an external source on the K terminal. It can be detected on the Y and Z terminals alternately as the contacts open close. Utility Industry convention generally dictates that the receiving device supplies the wetting voltage to the sending device (relay to meter, energy control system to relay). This is not necessarily true with the Process Control Industry or Energy Management Industry. 21

22 Contact Forms Form A Normally open 2 wire contact; SPST Form C A set of contacts consisting of one form A and one form B with a single common contact ( K ); SPDT. One contact breaks before the other makes. Break Before Make Contact Forms Form A 2 wire, SPST, Normally Open 22

23 Contact Forms Form C 3 wire, SPDT Break before Make Each change of state is a pulse Recommended for applications where no overlapping of contacts can be tolerated 2-Wire vs. 3-Wire Systems 2 wire systems (Form A) historically lacked immunity to induced noise because there is a period of zero voltage between pulses when noise may occur, causing false triggering of pulses. 3 wire systems (Form C) are much less prone to noise because a signal (a voltage) is always present. Always one energized, never both 23

24 2-Wire vs. 3-Wire Systems 3 wire systems have Form C contacts 2-Wire vs. 3-Wire Systems Most 2 wire systems have normally open contacts (Form A) only Normally closed (Form B) are rare 24

25 Contact Output Devices Mercury Wetted Electromechanical Relay Solid State Low Power Opto MOS SSR Solid State High Power Opto MOS SSR Relay Terms to Know Latching Relay A relay that will stay in the last position it is in when voltage is removed; also called a Bi Stable Relay two stable states Non Latching Relay A relay with one stable state; also called Monostable. The Normally Closed contact returns to the closed state in absence of power; (Current can flow) The Normally Open contact returns to the open state.(no current flow) 25

26 More Relay Terms Polarized Relay Uses +Vdc and Vdc alternately to simulate 3 Wire system using only two wires. Generally requires a specific purpose transmitting and receiving relay for use in sending pulses over relatively long distances. Used a polarity reversing scheme to latch and unlatch a latching relay Info Needed for Pulse Metering Applications Type of meter, including Ke or Kh, voltage & current ratings CT & PT ratings and ratios Typical and Maximum kw demand Interval length usually 15 minutes Required contact types A or C Desired Pulse Rate or Resolution Programming limitations: Maximum number of pulses per interval Pulse capacity or the maximum pulse acceptance rate of the receiving equipment: Maximum number of pulses per second 26

27 Isolation Relays Isolation relays are pulse repeating relays that provide an additional level of electrical protection between the device that originates a contact closure (such as utility owned meters with KYZ pulse output) and the receiving device (such as a customer owned energy management or monitoring equipment). They can additionally act as a pulse splitter or pulse duplicator to send one KYZ pulse output from the pulse initiator in the meter to multiple isolated & independent devices, such as RTU s, scada systems, recorders, EMS etc. Isolation Relay Types Isolation Relays are divided into two basic types: Line Wetting Voltage These were the original isolation relays that used line voltage across the KYZ metering output to drive the input of the isolation relay. Not recommended. Low Voltage Wetting Voltage These have a small transformer isolated DC power supply included in the relay to generate a +12 to +24VDC wetting voltage and is current limited for internal short circuit protection. Using a transformer isolated power supply adds a second dielectric or isolation barrier to the application. 27

28 Why do we use these devices? 1. Protection: prevent possible damage to meter To keep the customer s voltage and current out of the meter Protect meter from Lightning; Protect customer equipment Adds a second dielectric barrier between the utility meter and the customer s equipment. Adds Fusing to the customer output circuit 2. Separate Line and ground potentials 3. Mitigate Ground rise problems between systems 4. Pulse Voltage conversion 5. Scale pulse value from one value to required value to reduce # of pulses Pulse Isolation Relay Application Meter with EPI Isolation Relay KYZ KYZ KYZ SCADA component Recorder or EMS 28

29 Pulse Isolation Relay Application Pulse Isolation Relay Circuit 29

30 Output Relay Types Low Power Silicon (Solid State) Relays lower current carrying capability (100mA), higher on state resistance, lower cost, more prone to lightning damage & noise; non latching, optically coupled, 2500V High Power Silicon (Solid State) Relays lower current carrying capability (750mA), lower on state resistance, higher cost, less prone to lightning damage & noise; non latching, optically coupled, 2500V. Mercury Wetted Relays have a reed relay encapsulated in a glass tube with a small amount of mercury around the contact point to prevent arcing or bounce when the contacts close; 2A current carrying capability, highly impervious to lightning damage; usually latching, 1500V. Special Notes MW isolation relays must be installed in a vertical position (within 30 degrees of vertical). Some isolation relays may have fuses for each output relay AND a slow blow input fuse (~.25.5 amp). Some relays offer redundant fusing so customer cannot defeat fuse with a large amperage fuse. 30

31 Selecting the Proper Isolation Relay Self contained (outdoor) or modular (indoor)? Input format (2 wire, 3 wire or field selectable)? Output format (2 wire, 3 wire, dividing type, or fieldselectable)? Sense Voltage (Line voltage or isolated low voltage wetting voltage)? Can the sending device accept non isolated line voltages? Cont.. Selecting the Proper Isolation Relay What is the minimum time the sending device s contact is made up (>25 ms)? (40pps) What is the minimum current the sending device can switch (>10 ma) to reliably operate the relay? What is the maximum output current the relay can switch (>100mA to <2 amps)? How many isolated dry contact outputs are required? (1,2,3,4 or 6) Highest Input to Output Isolation voltage you can get: 2500V vs. 3750V 31

32 Typical Specifications Inputs Pulse Inputs: 1 4; Type: Form A,C Power Supply Voltage: 120V 277V Power (Burden) ~2 w Max Pulse Rate accepted (transitions/second) Surge Suppression(VAC) Internally generated +13VDC wetting voltage Outputs Number (1 6) Type (Dry contact, Mercury Wetted or Solid State, Form A,C) Maximum Contact Voltage & Current Contact VA Rating Contact Life (# operations at maximum ratings) Surge Suppression (VAC) Current Limiting or Fusing Typical Specifications Contact On State Resistance 50 milliohms max for MW 20 ohms typical for LP SSR 1.7 ohms typical for HP SSR Insulation Resistance (50 megohms typical) Operate and Release Time (Typically 1 to 10 milliseconds) Maximum Dielectric Voltage 1500V for MW V for SSR 32

33 Isolation Relay Selection Typical Self-Contained (Outdoor) Unit Isolation Relay Selection Typical Modular Relays Form C (3 wire in 3 wire out) Low Voltage Select number or low voltage outputs desired 33

34 Isolation Relay Selection Totalizers / Pulse Accumulators Multiple Inputs One or more outputs Programmable input & output values 5 Take-Aways 1. A pulse is a switch closure SPDT 2. Each switch closure is a representation of a fixed amount of energy which has gone past the meter 3. Dry contacts must be wetted with a voltage generally from the pulse receiving ( downstream ) device 4. 2 wire values are double 3 wire values 5. Isolation Relays can protect your meter and your customer s equipment: Think separation of circuits. 34

35 Questions & Answers For Copy of Presentation, please send to or give me your business card 35